Dear …
RE: __(Name of Project/Program)__
I want to take this opportunity to congratulate __(name of department)__ for a first-rate job done in designing the __(type project/program)__. The commitment each team member exhibited with their individual contributions to __(this project/program name)__ was quite impressive. Each one of them proved to be exceptionally accommodating on this __(case/project/etc)__, willing to help in anyway to expedite the process.
The overall dedication demonstrated by your team resulted in __(project/program)__ design that is nothing short of excellence in quality. I commend all of you for an outstanding job. Well done!
Sincerely,